We have recently observed that the integrin-linked signaling pathway (ILK) is active in replicating intimal smooth muscle cells of balloon catheter injured arteries. The focus of this proposal is to determine if the activation of this signaling pathway is responsible for the expression of cyclin Dl and ultimately for the replication of intimal SMC. Experiments are designed to examine the downstream targets of ILK in injured rat arteries and will include the activation of GSK-3, the expression and nuclear location of f3-catenin and the activation of the Lef/B-catenin sites on the cyclin Dl promoter. The next aim will identify the upstream regulators of ILK and experiments are proposed to investigate the importance of integrin activation and the P13K pathway. Blocking antibodies will be used to inhibit B1 and B3 integrin activation in injured arteries and ILK activity measured. Wortmannin will be used to inhibit the P13K pathway in replicating intimal SMC and ILK activity quantitated. The last aim will use mice with the ILK gene flanked by Lox sites and breed them with mice expressing smooth muscle specific Cre mice. The resultant off spring will have ILK deleted in SMC and these mice will be then used for injury studies. Cyclin Dl expression and SMC replication will then be measured at a various times after carotid artery injury. Strategies are proposed to circumvent the possibility that such mice are not viable. Finally an adenovirus expressing dominant negative ILK will be used to transfect intimal SMC and both cyclin Dl expression and intimal SMC replication measured. These studies will allow us to demonstrate the importance of the ILK-signaling pathway for the expression of cyclin Dl and the replication of intimal SMC.